1. Field of the Invention
This invention is a directed to a message routing protocol for a mobile ad hoc network (MANET).
2. Discussion of the Known Art
Mobile ad hoc networks or MANETs are self configuring networks in which a number of mobile nodes may interconnect with one another via wireless links. The locations of the nodes with respect to one another, i.e., the topology of the network, may therefore change rapidly particularly when such networks are deployed in emergency situations or in military operations. Early implementations of MANETs were referred to as “packet radio” networks. Today, for example, the so-called “Wi-Fi” wireless protocol specified by IEEE 802.11x also includes an ad-hoc mode that enables message traffic to be handled among a local “cloud” of wireless devices (e.g., Wi-Fi equipped laptops) in the absence of a wired infrastructure.
In a military joint airborne environment, efficient networking requires operational flexibility with ad-hoc management of networking resources. It is also important to maintain low overhead so that bandwidth remains available for communication among users. Network users may also require end-to-end quality-of-service (Qos) support to manage latency, stability, and response time. Other desirable operational requirements may include security, adaptability, interoperability, speedy join time, and rapid network formation.
Request for Comment (RFC) No. 3626 (October 2003) discloses a so-called Optimized Link State Routing (OLSR) protocol for mobile ad hoc networks. A given node in the network selects a subset of neighboring nodes each of which is within hearing distance (one hop) from the given node. The nodes of this subset are referred to as multipoint relays (MPRs), and are situated so that when they retransmit a message broadcast by the given node, the message will be received by all nodes that are two hops away from the given node. Neighbors of the given node that are not in its MPR set do not forward messages received from the given node, however. Although the MPRs may help to reduce redundant retransmissions of network updates, a fast changing topology is likely to trigger an excessive number of updates and thus propagate increased control overhead throughout the network. See also US Patent Application Publication 2002/0145978 (Oct. 10, 2002) which discloses a routing protocol for mobile networks, including the discovery of a route to a destination node that is beyond two hops from a source node wanting to send a message.
An Internet Draft entitled “The Zone Routing Protocol (ZRP) for Ad Hoc Networks” (July 2002) discloses a hybrid protocol having both proactive and reactive components. It is suggested in an implementation of ZRP that OLSR be used for proactive routing, and that Ad-Hoc On-Demand Distance Vector Routing (AODV) be used for reactive routing. Like OLSR, ZRP is not readily adaptable to rapid changes in network topology, however.
U.S. Pat. No. 5,652,751 (Jul. 29, 1997) discloses an architecture for mobile radio networks with dynamically changing topology. A network is partitioned into physical subnets each of which includes a number of nodes in close proximity to one another. Each node in a physical subnet is affiliated with a corresponding node in each of the other physical subnets, thus defining a number of virtual subnets. A message is routed from a source node to a remote destination node in the network, by forwarding the message through nodes that are members of the same physical subnet during a first phase of two alternating transmission phases, and through nodes that are members of the same virtual subnet during the second transmission phase. Although the patent contemplates network routing in a fast changing topology, it requires complex address management, physical partition of subnets, and hardware/spectrum changes.